Antenna structure



Sept. 14 lss. q f 1,599,453

Y H. A. AFFEL ANTENNA STRUCTURE Impedance zyue IN V EN TOR.

Wj TTORNE Y Patented Sept. v14, 1926.

UNITED srATss 4HERMAN Virais' PATENT O F'Fics. 11

A. ARIEL, OF BROOKLYN, NEW YORK, AssIGNoR'TO AMERICAN TELE-PHONE y ANDTELRCRAPH COMPANY, A CORPORATION or NEW YORK', f

ANTENNA STRUCTURE. 'y

yApplicant@ iea'yrune 24,1922. seria1No`.57o,54o.

.This invention relates, to antenna struc-- tures, and particularly tomeans for adapting a .long antenna for the efficient voperation with aplurality Aof .different wave lengths. l

For some time past it vhas beenlnown that long horizontal antennaeareparticularly well adaptedA for the'reception of signals, since they,possess a high degree of diin' zu.)

rectivity. On the other hand, a particular long antenna structure 1sadapted to receive only the long wave lengths efficiently, which iconsequently precludes its use forysatisfac-v tory shorter wave lengthreception. i. y

It is the objectv of thisinvention-to ypro-y vide means for renderingalong antenna structure capable of functioning efficiently with waves of-ae vplurality "of different lengths.

This invention will be better understood from the followingdescriptionwhenfread in connectiongwith the attached drawing, of which Figure -lshows the invention einbodied in an antenna of the dumb-bell type; Fig.2 shows schematic equivalent circuitsof the arrangement shown in Fig. l,Fig. showsthe invention,embodied in an anten-V na of the inverted ltype;Fig. l v,snows schematic equivalent circuits of the arrangei ment inFig. 3; and Figs. 5 and 6 are groups of curves which serve to 'describe`the manner in which the invention functions.'

In Fig. l, l represents an antenna of the long horizontal type, 4thedistant yends'of which may if desired be terminated through resistancesR04 and RO', which, as described in my copendingapplication, vSerial No.585,- 435, filed August:l ,31, 1922, simulate the characteristicimpedance ofthe antenna, Counected latthe lmidpointyof the antenna bymeans ofthe inductive coupling 2 is ak plurality of receivingcircuitswhich are rendered selective to particular,frequencies or bandsofr frequencies by means of the filters F10 F11 and F12.y The antenna vl has .connected therewith` at predetermined points throughout. its`.length the` ltersF,L and F1, Fl and F2. .Although four yfilters areAshown v connected withk the antenna, the invention is 'not limitedjtothe v particular ,number'showin since anynurnber of lters may beconnected, depending upon the number of wave lengths which vthe antennais designed to receive.

As has been briefly referred toy heretofore,

every antenna circuit should havek a partie'- ular optimum length forthe particular wave length or range of wave lengths intended to bereceivedin order to attain efficient ,operation yof vthe system.. Myinvention. consists ininserting in the antenna structuregatpredetermined locations ya .plurality of lowjpass .filters arranged asshown in Fig. 1 in groups of two each, which-.serve to termif nate theantenna structure vfor 'particular yfrequencies at the pointsAwhereinthey are inserted and render the intervening section of antenna'adapted vfor the reception of a `particular frequency. 'lhus,vforexample, vthe filters F1 and. F1l would have-.theatltennation-frequency characteristic represented lby the curve d, invFig.y vThisjis the characteristic` for a lowTpass filtenhaving acut-off. point at the frequency f1. It will .be seen, therefore, that byinserting ya group of two of these filters inthe antennay v1 .atapredetermined point, depending uponthe length of a wave having afrequency futhemore, since the filtersF1 andFl are ofthe low-pass type,they will transmit `readily frequencies below their cut-off frequencies.

.Consequently they. do not terminate the an-` vantenna is, in effect,terminated at thesaio. points for the said frequency. Furthershows acut-odffrequencyfz. Accordingly, these filters will serve to terminateythe anv tenna forxthe frequency f2, and therefore render the section oftheantenna betweenl F2 and F2 adapted to..receive that fre?v quency orbandl of frequencies which are `above frf Other groups of'iiltershavingthe characteristics represented by'y f vand g in Fig. ,5 could beinserted in the antenna 1 which would serveto` terminate vthe anten/na'at otherpoints and render rvthe intervening antennastructure suitableforthe reception of other/,frequencies than those shown. Furthermore,the antenna between'the terminating resistances RO landfRO ywould,of

course, .be adapted to receive still another andrdifferent frequencyfrom any hereto-fore referred to.

The

ters as .shown in Fig.. l. is to render the andect, therefore,Offinserting the -ltennaA structure highly efficient for the receptionof three different frequencies. The complete action attained bythestructure shown in Fig. l may in a sense, be considered lequivalentt0 that whichrwould obtain for three separate antenna structures, eachspecifically designed to function fora definite wave length range.rllhis is clearly shown in the equivalent circuit 'diagrams of Fig. 2,where the structure a represents the antenna` 1,' which for frequenciesf1 or greater is 'effectively terminated by 4the lfilters -F and F1.Siniilarly, the structure represented by b represents the antenna leffectively terminated by the filters lf2 and F2', which is eicie'nt forthe reception of frequencies )f2 and greater, and the struc- Yturerep-resentec'l by c of F ig. v2 represents the antenna l as terminatedby the resistantes `ith-"and R0.

The arrangement shown in Fig. 3 represents the embodiment of theinvention in an inverted L antenna. F2 inserted in theantenna i serve to`terininate this-antenna in the saine manner in which 'they function inconnection with'the antenna shown in Fig. yl. The effect of introducingthese `filters is to render the anltenna structure of Fig. 3 terminatedat the points wherein -they are inserted, which, in effect, makes theantenna suitable for the reception of -three di'erent wave lengths, asclearly Ashown lthe diagrams in Fig. 4

Although i'ny invention is not limited to the ,'use of yany particulartype of filter to jeffect 'the discontinuity 'of the fantenna structureitself for particular frequencies, l find that the type of network showndiagrammatically in Figs. l and 3 which includes re'sistance'elements inits malreup is particularly well suited for this purpose, since it 'maybe 'designed 'to possess substan tial'ly luniform impedance throughoutthe lentire range of frequencies, and therefore, -in effect, serves toterminate the antenna at the point wherein it is inserted by aniinpedancejeqiial to the characteristic impedance 'of ithe antenna :forthe cut-off frequency of ythe particular filter. rlhis is clearly 'shownin Figs. 5 and G.L Thus in F ig. f6 the curves d', e, f vand g'represent characteristie impedance-frequency actions of the normaltypeofc-filter, the attenuationfrequency lcharacteristics of which arerepren sented by -thefcurves d, e, fand g of Fig. 5,

that is to say, in 'the 'normal'non-dissipative type of filter :theimpedance would either increasera'pidly at the cut-olf frequency inAlike manner, -as the attenuation does or wouldy decrease rapidly ytoapproach lzero, 'depending on the particular type of terminationemployed.v In filters of the type-represented, for example in Fig. l,the -inipech 'ance fdoes not 'vary as the cut-oil' frequency 'isreached, 'but remains substantially unirlhe. lfilters F1 and formthroughout almost any range lof frequency. They use of filters 'of thistype, therefore, has the effect of terminating the antenna structure atthe point wherein they are inserted by means of an impedance equal tothe characteristic impedance of that pari. of the antenna includedbetween the two filters of the group, which, of course, is high-lydesirable, since it avoids creating the effect of an open-ended antennafor the particular frequencyl for which the intervening antennastructure is intended to receive.

For the purpose of making the invention clear and distinct it has beendescribed fas embodied in anantenna having receiving apparatusassociated therewith.` The invention, however', is not limited to` areceiving antenna since it is equally well adapted for the purpose oftransmitting, 'and accordingly the apparatus shown and described' asreceiving apparatus may also be `considered as transmitting apparatus.

Although this invention has been 'disclosed embodied in a particularforni and arrangementof parts, it isto be understood that it is capableof embodiment i-n other and different forms within'the spirit yand scopeof the appended claims.

lli/hat is claimed is:

l. An antenna, comprising ,a conductor of such length as tovvefficiently receive waves of predetermined length, and a Vfilterhavinga fined cut-elf point l'connected 'with thesaid conductor andeffectively 'terminating the conductor at the point of connection of theW0 said filter for frequencies `'above the cut-'off point, the saidpoint of connection being so Ychosen that the portion of the saidantenna between the said poi-nt of connection of the lte'r and pointofc'onnection of a lterini- T105 nal circuit will have the optimumlength foi-.frequencies above the cut-off frequency of the filter.- y

2. An antenna, ycomprisin'gra conductor ofk such `length as toeflicfiently respond t0 1l-l0 waves of a predetermined length, and a'plurality of filters each connected with the said conductors atdifferent places .between thee'nds thereof, each fiilterhaving ia 'fiXedcut-off point whichffor leach filter, is 'dif- "11'5 ferent from 'thatof the others, Lto effectively terminate. the conductor lvateach of a1'plurality `of .points for frequencies above the "cut-ofia poin'tof theiilter,eac'h point o'f-'connection of the said' filters bein-g so chosen120 `that the portion of the antenna between the point #of rconnectionof afpafrticular fiilter 'anc the -end adjacent to the terminal-circuitwill have the optimum length lfor frequenciesy 'above fthe cut-olf'frequency fo'ff the 125 particular ffilte'rf 3. An antenna, comprisinga conductorof 'such lengthas to efficiently respond towaves f filters ofthat particular group.

nected with the said conductor at different places between theterminating point of the antenna and the ends thereof, each filterhaving a fixed cut-o point and the filters of each group having the samecut-off point which is different from that of the otherA groups offilters, the filters of each group being symmetrically placed uponopposite sides of the terminating point of the antenna, each point ofconnection of the said lters being so chosen thatv the portion of theantenna between two filters of the same group will have the optimumlength for frequencies above the cut-off frequency of the definiteintervals between the terminating point and the distant end of the saidantenna, the filters more distant from the said terminating point havingav lower cut-off point than those nearer thereto.

6. An antenna comprising a horizontal conductor having the distant endsgrounded through resistances simulating the characteristic impedance ofthe antenna and having a plurality of pairs vof filters inserted thereinbetween the terminating point and the outer ends of said antenna, andsym metrically disposed'on eachside of the said terminating point.

7 In a radio signaling system, the combination with an antenna of aplurality of low-pass filters having different cut-off points and amulti-frequency terminal apparatus, the said filters being connectedinto the said antenna between the point of connection thereto ofthe saidapparatus and the distant end and-'so disposed that those more distantfrom the said apparatus have lower cutoff points than those nearerthereto. u f

8. In a radio signaling system, the coinbination with an Aantenna havingits outer ends grounded through a resistance simulating thecharacteristic impedancepof the antenna of a plurality of pairso'fLlow-pass filters, the said pairs having different cutoff points7 andmulti-frequency terminal apparatus connected with the said antenna, the

said filters being symmetrically disposed on each side of the point ofconnection of the said apparatus to said antenna and so arranged thatthe vmore distant ones have lower cut-ofi' points than those nearer thesaid apparatus. Y

9. A horizontal 'antenna having a plurality of filters eachhaving adifferent -frequency cut-ofi point, the said filters beingconnected'therein between the terminatingl point of said antenna and anouter end thereof, the distance vbetween each of said filters and theterminating point of the antenna beingthe optimum length of the antennafor the frequency at whichthe particular filter cuts off.

10. A horizontal antenna having a plul rality'of pairs of' filters, eachpair having a different frequency cut-ofiE point, the filters of eachpairbeing vconnected kwith the said antennaat points which are uponopposite sidesof the terminating point of the said antenna and thelength of the antenna between eac-h pair of filtersbeing the optimuinlength for the frequency at which the y particular pair of filters cutsoff.

In testimony whereof, I have signed my name to this specification*` this23rd day of June 1922.

- HERMAN A.y AFFEL.

